Welding electrodes with functional coatings

Abstract

The disclosed technology relates generally to welding electrodes, and more particularly to consumable welding electrodes having functional coatings. In one aspect, the welding electrode includes a core wire having a base metal composition and two or more coatings covering at least a portion of the core wire. The two or more coatings include a conductive coating including one or more conductive elements or compounds in addition to or other than copper (Cu). The two or more coatings further include an additional functional coating including one or more additional elements or compounds adapted to reduce friction of the welding electrode, stabilize an arc formed from the welding electrode, adjust the microstructure of the weld metal formed from the welding electrode, and / or adjust the surface tension of molten droplets formed from the welding electrode. In another aspect, a method for manufacturing a welding electrode includes providing a core wire having a base metal composition and forming two or more coating layers.

Description

[Technical Field]

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63,374,940, filed September 8, 2022, entitled "WELDING ELECTRODE WITH FUNCTIONAL COATINGS," and is a continuation-in-part of U.S. Provisional Patent Application No. 17 / 930,993, filed September 9, 2022, entitled "WELDING ELECTRODE WITH FUNCTIONAL COATINGS," which claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 261,462, filed September 21, 2021, entitled "WELDING ELECTRODE WITH FUNCTIONAL COATINGS," the contents of which are incorporated herein by reference in their entireties.

[0002] The disclosed technology relates generally to welding electrodes, and more particularly to consumable welding electrodes having a functional coating on a core wire. [Background technology]

[0003] Various welding techniques utilize a consumable welding electrode that serves as a source of weld metal. For example, in metal arc welding, an electric arc is created when a voltage is applied between a consumable welding electrode, which serves as one electrode, advancing toward the workpiece, and the workpiece, which serves as the other electrode. The arc melts the tip of the metal wire, thereby creating droplets of molten metal electrode that deposit on the workpiece to form the weld metal, or weld bead.

[0004] The technical and economic demands on welding technologies continue to become more complex, with the need for greater manufacturing flexibility and the need for greater mechanical performance coexisting. Additionally, optimizing one performance parameter of the weld metal may compromise another. Some welding technologies attempt to address these competing demands by improving consumables, for example, by improving the physical design and / or composition of the consumable electrode. The disclosed technology addresses the need for improved consumable welding electrodes with functional coatings. Summary of the Invention [Means for solving the problem]

[0005] In a first aspect, a welding electrode includes a core wire having a base metal composition and two or more coatings covering at least a portion of the core wire. The two or more coatings include a conductive coating including one or more conductive elements or compounds in addition to or other than copper (Cu). The two or more coatings further include an additional functional coating. The additional functional coating includes one or more additional elements or compounds adapted to reduce friction of the welding electrode, stabilize an arc formed from the welding electrode, adjust the microstructure of a weld metal formed from the welding electrode, and / or adjust the surface tension of a molten droplet formed from the welding electrode.

[0006] In a second aspect, a method of making a welding electrode includes providing a core wire having a base metal composition and forming two or more coatings of the first aspect.

[0007] In a third aspect, a welding electrode includes a solid core wire having an iron (Fe)-based base metal composition and a conductive coating formed on the solid core wire. The conductive coating includes one or more conductive elements or compounds in addition to or other than copper (Cu). The welding electrode further includes an additional functional coating formed on the conductive coating and including one or both of elemental antimony (Sb) and one or more Sb oxides.

[0008] In a fourth aspect, a welding electrode includes a solid core wire having an iron (Fe)-based base metal composition and two or more coatings covering at least a portion of the core wire. The two or more coatings include a conductive coating formed on the solid core wire that includes one or more conductive elements or compounds in addition to or other than copper (Cu). The two or more coatings further include an additional functional coating having a porous structure formed on the conductive coating and including antimony (Sb). [Brief explanation of the drawings]

[0009] [Figure 1] 1 illustrates an arc welding system that can be used in conjunction with a consumable electrode according to embodiments disclosed herein. [Figure 2] 1 illustrates a welding process using a consumable electrode according to embodiments disclosed herein. [Figure 3] 1 illustrates a coated welding consumable electrode according to an embodiment. [Figure 4A] 1 illustrates a coated welding consumable electrode including two or more coatings, according to an embodiment. [Figure 4B] 1 illustrates a coated welding consumable electrode including three or more coatings, according to an embodiment. [Figure 5] 1 illustrates a method for manufacturing a coated welding consumable electrode, according to an embodiment. [Figure 6A] 1 shows a weld metal formed using a conventional consumable electrode. [Figure 6B]1 illustrates a weld metal formed using a consumable electrode having a functional coating according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Some welding electrodes have two main components: a core wire or rod and a sheath or coating. The core contains the base alloying elements of the weld metal. The coating can include various materials that provide various functionalities. For example, coatings may function to shield the weld metal, stabilize the arc, alloy the weld metal for various physical properties, slag for flux, reduce gas pockets in the weld metal, improve electrical conductivity or insulation, protect from the environment, lubricate for feeding, and provide an attractive appearance, to name a few.

[0011] Some conventional solid welding wires are coated with a copper-containing coating on the surface of the wire to increase the electrical conductivity and corrosion resistance of the wire and welding nozzle, and to reduce friction with the feed hose or welding nozzle. However, during the welding process, some of the copper can undesirably dissolve into the weld. Copper contamination of the weld can cause "copper cracking" or reduce the mechanical properties of the weld joint, especially impact toughness and elongation at low temperatures. Copper can also oxidize and form copper particles that leak into the air, which can be harmful to human health if inhaled. The production of copper-coated welding wire can also produce waste acid and environmental pollution. Therefore, there is a need for a coated wire that at least reduces or eliminates copper from the coating of welding electrodes while maintaining functional benefits.

[0012] To address these and other needs, embodiments disclosed herein relate to a welding electrode including a core wire having a base metal composition and two or more coatings covering at least a portion of the core wire. The two or more coatings include a conductive coating including one or more conductive elements or compounds in addition to or other than copper (Cu). The two or more coatings further include an additional functional coating including one or more additional elements or compounds adapted to reduce friction of the welding electrode (friction modifier), stabilize the arc formed from the welding electrode (arc stabilizer), modify the microstructure of the weld metal formed from the welding electrode (microstructure modifier), and / or modify the surface tension of molten droplets formed from the welding electrode (molten weld metal surface tension modifier).

[0013] Arc welding process for welding with electrodes having functional coatings - Patent Application 20070122997 Arc welding is one of several fusion processes for joining metals. The application of intense heat causes the metal at the joint between two parts to melt, either directly or, more commonly, to mix with an intermediate molten filler metal.

[0014] An arc welding system 100 usable in conjunction with embodiments disclosed herein is shown in FIG. 1. A power system 110, including an AC or DC power source and controls, is connected by a work cable 114 to a workpiece 102 to be welded and by a "hot" cable to an electrode holder 118 in electrical contact with a welding electrode 106. An arc is created across the gap between the workpiece 102 and the welding electrode 106 when the tip of the current-carrying circuit and electrode contacts the workpiece 102 and then pulls away while still in close proximity. The electric arc can be created between the welding electrode 106, which may be a consumable electrode acting as one electrode (e.g., an anode (+) in DC), and the workpiece 102, which acts as the other electrode (e.g., a cathode (-) in DC). After the arc is initiated, a plasma 108 is maintained, including neutral and ionized gas molecules, as well as neutral and charged clusters or droplets of material from the metal wire vaporized by the arc. The welding electrode 106 advances toward the workpiece 102, depositing molten droplets of metal wire onto the workpiece, thereby forming a weld bead or weld metal. The arc can generate temperatures as high as approximately 6500°F at its tip. This heat melts both the workpiece 102 and the welding electrode 106, creating a pool of molten metal, sometimes called a "crater." The crater solidifies behind the electrode as it moves along the joint. Upon cooling and solidification, a metallurgical bond is formed. Because the joint is a mixture of metals, the final weldment can have mechanical properties, such as strength, comparable to or substantially the same as the metals of the components of the workpiece 102. This is significantly different from non-fusion joining processes (e.g., soldering, brazing, etc.), in which the mechanical and physical properties of the base material may not be comparable to those of the workpiece 102 at the joint.

[0015] Hot metals tend to chemically react with elements in the air (oxygen and nitrogen). When the metal in the weld pool comes into contact with air, oxides and nitrides can form, which can adversely affect the strength and toughness of the weld joint. Therefore, some arc welding processes provide some means of covering the arc and weld pool with a protective shield of gas, steam, and / or slag. This is called an arc shield. This shield reduces or minimizes contact between the molten metal and the air. The shield can also improve the weld. One example is a flux, which may contain a reducing agent for the weld metal.

[0016] In welding, the arc not only provides the heat necessary to melt the electrode and base metal, but under certain conditions must also provide a means to transport the molten metal from the tip of the electrode to the workpiece. Several mechanisms exist for metal transfer. Examples include surface tension transfer, in which a droplet of molten metal contacts the molten metal pool and is drawn into it by surface tension, and the spray arc, in which a droplet is ejected from the molten metal at the electrode tip by an electric pinch effect that propels it into the molten pool.

[0017] If the electrode 106 is a consumable electrode as disclosed herein, the tip melts due to the heat of the arc, and molten droplets break off and are carried to the workpiece 102 via the arc column. Arc welding according to the embodiments described herein, in which the electrode burns through and becomes part of the weld, is referred to as metal arc welding. This is in contrast to carbon or tungsten (TIG) welding, in which there are no molten droplets forced across the gap and onto the workpiece. A filler metal is melted into the joint from a separate rod or wire. Much of the heat generated by the arc is transferred to the weld pool using the consumable electrode, which improves thermal efficiency and reduces the heat-affected zone.

[0018] Arc welding can be done with direct current (DC) or alternating current (AC), with the rod either positive (DCEP) or negative (DCEN). The choice of current and polarity depends on the process, the type of electrode, the arc atmosphere, and the metals being welded.

[0019] In processes using consumable electrodes, the electrode or wire melts, thereby providing additive metal that bridges the gap and forms a weld joint joining two metal workpieces. Welding processes using consumable electrodes include, among others, shielded metal arc welding (SMAW), gas metal arc welding (GMAW) or metal inert gas (MIG) welding, flux cored arc welding (FCAW), metal cored arc welding (MCAW), and submerged arc welding (SAW). Welding processes using consumable welding electrodes can be performed in direct current electrode positive (DCEP) mode, direct current electrode negative (DCEN) mode, or alternating current (AC) mode. In DCEP mode, direct current is used, and the wire is connected to the positive terminal of the power source and the workpiece(s) or plate(s) to be welded are connected to the negative terminal, while vice versa when welding in DCEN mode. In AC mode, the wire and the workpiece(s) or plate(s) to be welded are periodically switched from positive to negative depending on the frequency. The terminal that functions as the positive electrode may be referred to as the anode, and the terminal that functions as the negative electrode may be referred to as the cathode. The following describes various consumable electrode-based welding processes that can be performed using oxide-coated welding wire according to embodiments.

[0020] 2 illustrates a gas metal arc welding (GMAW) process 200, sometimes referred to as a metal inert gas (MIG) welding process, that can be used in conjunction with embodiments disclosed herein. The GMAW process uses a continuous solid wire electrode 106 for the filler metal and an externally supplied gas (typically from a high-pressure cylinder) for shielding. The electrode 106 may be mild steel or stainless steel and, according to various embodiments, can be coated with a thin coating layer, which may include two or more coatings, including an electrically conductive coating and an additional functional coating adapted to reduce friction of the welding electrode (friction modifier), stabilize the arc formed from the welding electrode (arc stabilizer), modify the microstructure of the weld metal formed from the welding electrode (microstructure modifier), and / or modify the surface tension of the molten droplets formed from the welding electrode (molten weld metal surface tension modifier). When an arc 108 is struck between the electrode 106 and the workpiece 102, both the electrode 106 and the surface of the workpiece 102 vaporize, forming droplets of metal that are transferred to the surface of the workpiece 102, thereby forming a weld pool 204 containing the metal of the coated electrode 106 and the metal of the workpiece 102. The welder may be configured for DC positive polarity. A shielding gas, typically carbon dioxide or a mixture of carbon dioxide and argon, protects the molten metal from the atmosphere. The shielding gas flows through the gun and cable assembly and out the gun nozzle along with the welding wire to shield and protect the molten weld pool. Molten metal can be highly reactive to atmospheric oxygen, nitrogen, and hydrogen when exposed to them. According to various embodiments, a welding electrode configured for the various welding processes described above, such as GMAW, includes a core wire having a base metal composition and two or more coatings covering at least a portion of the core wire. As described herein, the two or more coatings include a conductive coating containing one or more conductive elements or compounds in addition to or other than copper (Cu). The two or more coatings further include an additional functional coating.The additional functional coating includes one or more additional elements or compounds adapted to reduce friction of the welding electrode, stabilize the arc formed from the welding electrode, adjust the microstructure of the weld metal formed from the welding electrode, and / or adjust the surface tension of the molten droplets formed from the welding electrode.

[0021] FIG. 3 illustrates a welding consumable electrode 300 according to various embodiments. The electrode 300 includes a core wire 304 and a coating 308. In some embodiments, the core wire 304 may include a suitable carbon steel, such as mild steel for GMAW. However, in other embodiments, the core wire 304 includes another metal or metal alloy. For example, in some embodiments, the core wire 304 may include stainless steel. The coating 308 coats the core wire 304 to provide alloying elements for the resulting weld metal and various additional non-alloy functionalities, as described herein. The chemical elements and compounds of the core wire 304 and coating 308 disclosed herein may be distinguished based on whether the constituent elements are incorporated as part of the weld metal alloy. Hereinafter, elements that are substantially incorporated into the resulting weld metal may be referred to as alloying elements, while elements that are not substantially incorporated into the resulting weld metal and that perform other functions, such as slag or gas formation or arc stabilization, may be referred to as non-alloying elements.

[0022] 4A and 4B show coated welding consumable electrodes 400A and 400B, respectively, according to some other embodiments. The electrodes 400A and 400B include a core wire 304 and a coating 308, and are configured similarly to the electrode 300A shown in FIG. 3, except that the electrodes 400A and 400B include multiple coatings. By way of example, the electrode 400A includes two coatings 308, including a first coating 308A and a second coating 308B. The electrode 400B includes multiple coatings 308, including a first coating 308A, a second coating 308B, and a third coating 308C. Furthermore, although not shown, the multiple coatings according to other embodiments may include n coatings, including coatings 1 through n.

[0023] As noted above, the weld metal may include the solidified metal of the workpiece and the metal of the consumable electrode. Because the amount of dilution or enrichment of elements in the weld metal due to the inclusion of the molten workpiece can vary considerably, unless otherwise indicated, the weight percentages of various elements and compounds in the weld metal disclosed herein refer to the weight percentages of the undiluted weld metal that would result if no dilution or enrichment had occurred from the workpiece.

[0024] Continuing with reference to FIGS. 3 and 4A-4B, in some embodiments, core wire 304 comprises a carbon steel composition, such as a mild steel composition. In these embodiments, various carbon steel compositions include Fe and one or more of C, Cr, Ni, Mo, V, Cu, Mn, and Si at concentrations greater than impurity levels. In some embodiments, core wire 304 comprises a low-alloy steel composition with an alloying element content of approximately 1.5% to 5% by weight. Additional elements may be present, which may be present at impurity levels. As described herein, impurity levels refer to the weight percentage of elements that are not intentionally introduced but are nonetheless present, and may generally be less than 0.05%. Impurities that are not intentionally added but are still present in core wire 304 include S, P, Al, Cu, N, Cr, Ni, Mo, V, Nb, and Ti. The balance of the weight of core wire 304 may be Fe. In some embodiments, the core wire 304 is formed from a mild steel composition known in the art according to a numbering system developed by the American Welding Society (AWS). For example, in some embodiments, the core wire 304 is formed from AWS A5.18 mild steel, AWS A5.28 mild steel, AWS, or D1.5 mild steel.

[0025] However, in other embodiments, core wire 304 comprises a composition other than a carbon steel composition. For example, in some embodiments, core wire 304 comprises a stainless steel composition. In these embodiments, various stainless steel compositions include Fe, at least 11% by weight Cr, and one or more of C and Ni at concentrations above impurity levels. In some embodiments, core wire 304 comprises at least 11% by weight Cr, or 8% to 30% by weight Cr. In some embodiments, core wire 304 is formed from stainless steel alloy compositions known in the art according to a three-digit numbering system developed by SAE International to classify stainless steel grades, including 100, 200, 300, 400, 500, 600, 900 series, etc. For example, in some embodiments, core wire 304 is formed from 308, 309, 316, or 410 steel.

[0026] 4A-4B, coating 308 includes a conductive coating including one or more conductive elements or compounds in addition to or other than copper (Cu) and an additional functional coating including one or more additional elements or compounds adapted to reduce friction of the welding electrode, stabilize the arc formed from the welding electrode, adjust the microstructure of the weld metal formed from the welding electrode, and / or adjust the surface tension of the molten droplets formed from the welding electrode. As described herein, either first coating 308A or second coating 308B of electrode 400A (FIG. 4A) or either first coating 308A, second coating 308B, and third coating 308C of electrode 400B (FIG. 4B) may be a conductive layer or an additional functional layer, in any order. Thus, although the conductive coating according to embodiments may be referred to as the first coating 308A of the electrodes 400A, 400B, being the innermost coating of the plurality of coatings 308, it will be understood that the conductive coating may also be the second coating 308B of the electrodes 400A, 400B, or the third coating 308C of the electrode 400B. Similarly, although the additional functional coating according to embodiments may be referred to as the first coating 308A of the electrodes 400A, 400B, being the innermost coating of the plurality of coatings 308, it will be understood that the additional functional coating may also be the second coating 308B of the electrodes 400A, 400B, or the third coating 308C of the electrode 400B.

[0027] conductive coating According to various embodiments, any one of the first coating 308A, the second coating 308B, and the third coating 308C (FIG. 4A or FIG. 4B) is a conductive coating including one or more conductive elements or compounds selected from the group consisting of magnesium (Mg), aluminum (Al), zinc (Zn), tin (Sn), chromium (Cr), platinum (Pt), silver (Ag), graphite, graphene, graphene oxide, and titanium (Ti).

[0028] According to various embodiments, the conductive coating functions to provide substantial electrical conductivity to the electrodes 400A, 400B such that a substantial amount (e.g., >10%, >30%, >50%, >70%, >90%, or a value within a range defined by any of these values) of the electrical current passing through the electrodes 400A, 400B during welding flows through the first coating 308A. In some embodiments, the one or more conductive elements or compounds are present in an amount and form such that the welding electrodes 400A, 400B have a lower electrical resistance compared to the core wire 304 without the conductive element or compound.

[0029] In some embodiments, the one or more conductive elements or compounds are present without Cu as part of the conductive coating or as part of any of the plurality of coatings 308. That is, in some embodiments, the one or more conductive elements or compounds may obviate the need to use Cu as part of a coating, for example, to provide the required conductivity, and Cu may be omitted from the plurality of coatings 308. In some other embodiments, the one or more conductive elements or compounds are present in addition to Cu as part of the conductive coating or as part of any of the plurality of coatings 308. That is, in some embodiments, the one or more conductive elements or compounds may supplement Cu, for example, as part of the same or a different coating, to provide the required conductivity.

[0030] The one or more conductive elements or compounds can significantly reduce or eliminate the need for copper as part of the coating in conventional coated electrode wire. Thus, according to embodiments, the one or more conductive elements or compounds can be present without or in addition to Cu. When present in addition to Cu, the one or more conductive elements are present in an amount greater than 50 at.%, 60 at.%, 70 at.%, 80 at.%, 90 at.%, or a value within a range defined by any of these values ​​of the sum of the one or more conductive elements or compounds and Cu. Thus, reducing the Cu content can advantageously reduce the adverse effects of copper cracking in the weld.

[0031] If present, Cu is present in an amount greater than 0.0005 wt.%, 0.0010 wt.%, 0.0020 wt.%, 0.0050 wt.%, 0.010 wt.%, 0.020 wt.%, 0.050 wt.%, 0.10 wt.%, 0.20 wt.%, 0.5 wt.% of the weight of the welding wire, or a value within a range defined by any of these values.

[0032] Additional Functional Coatings According to various embodiments, any one of the first coating 308A, the second coating 308B, and the third coating 308C (FIG. 4A or FIG. 4B) is an additional functional coating that includes one or more of a friction modifier, an arc stabilizer, a microstructure modifier layer, and a molten weld metal surface tension modifier, as described below.

[0033] During welding, the welding wire travels from the drum or spool, through the conduit, inlet guide, and feed roll, into the gun, through the liner, and out through the contact tip. Therefore, various frictional forces must be overcome to achieve uniform and efficient wire feeding. High levels of friction between the welding wire and the contact surfaces of the welding system can cause irregular wire feeding, vibration, burnback, and ultimately bird nesting, which can significantly disrupt production. To reduce the fractional force between the welding wire and the various contact surfaces of the welding system, according to some embodiments, the additional functional coating includes a friction modifier. The friction modifier includes one or more additional elements or compounds adapted to reduce friction of the welding electrode 400A. 400B. According to various embodiments, the one or more additional elements or compounds adapted to reduce friction of the welding electrode are selected from the group consisting of graphite, metal sulfides, polytetrafluoroethylene, graphene, and graphene oxide. When the one or more additional elements or compounds include a metal sulfide, the metal sulfide may include molybdenum disulfide (MoS2) or tungsten disulfide (WS2). Some metal sulfides, such as MoS2 and WS2, advantageously have a layered structure that makes them particularly suitable as lubricants. When present, the one or more additional elements or compounds adapted to reduce friction are present in an amount and form such that the wire feed force for feeding the welding wire through the wire liner is reduced by 30%, 40%, 50%, 60% or more, or by a value within a range defined by any of these values, compared to the wire feed force for feeding a core wire that does not include the one or more additional elements or compounds adapted to reduce friction.

[0034] Air does not have sufficient conductivity to maintain a stable arc. Therefore, there is a need for a coating composition that provides a stable plasma for current flow with reduced voltage fluctuations. To at least partially address this need, according to various embodiments, the additional functional coating includes an arc stabilizer. The arc stabilizer includes one or more additional elements or compounds adapted to stabilize the arc formed from the welding electrodes 400A, 400B. According to various embodiments, the one or more additional elements or compounds adapted to stabilize the arc are selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), cerium (Ce), barium (Ba), and radium (Ra). When present, the one or more additional elements or compounds adapted to stabilize the arc are present in an amount and form such that one or both of the oxygen and nitrogen contents of the weld metal formed from the welding wire are reduced by 30%, 40%, 50%, 60% or more, or a value within a range defined by any of these values, compared to the weld metal formed from a core wire that does not include the one or more additional elements or compounds adapted to stabilize the arc. Advantageously, the reduced amount of oxygen and nitrogen absorbed in the weld results in reduced formation of oxides and nitrides that can be crack initiation sites and reduce the impact toughness of the weld.

[0035] Various mechanical properties of the weld metal, including hardness and impact toughness, are largely determined by its microstructure, which in turn is determined in part by its chemical composition. According to some embodiments, the additional functional coating includes a microstructure modifier to provide a desired microstructure from the steel-based composition of the core wire. The microstructure modifier includes one or more additional elements or compounds adapted to modify the microstructure of the weld metal formed from the welding electrode 400A. 400B. According to various embodiments, the one or more additional elements or compounds adapted to modify the microstructure are selected from the group consisting of titanium (Ti), zirconium (Zr), nickel (Ni), boron (B), molybdenum (Mo), and niobium (Nb). When present, the one or more additional elements or compounds adapted to modify the microstructure of the weld metal are present in an amount and form such that the impact toughness of the weld metal formed from the welding wire is 30%, 40%, 50%, 60%, or more higher than that of a weld metal formed from a core wire that does not include the one or more additional elements or compounds adapted to modify the microstructure.When present, the one or more additional elements or compounds adapted to modify the microstructure of the weld metal are present in an amount and form such that the ductile-to-brittle transition temperature of the weld metal formed from the welding wire is at least 30%, 40%, 50%, 60%, or more lower than that of a weld metal formed from a core wire that does not include the one or more additional elements or compounds adapted to modify the microstructure.

[0036] Various productivity parameters, such as the travel speed for forming the weld metal, can be determined in part by the surface tension of the molten droplets of weld metal. To provide a desired molten weld metal surface tension, according to some embodiments, the additional functional coating includes a molten weld metal surface tension modifier. The molten weld metal surface tension modifier includes one or more additional elements or compounds adapted to adjust the surface tension of the molten droplets of weld metal formed from the welding electrode 400A. 400B. According to various embodiments, the one or more additional elements or compounds adapted to adjust the surface tension are selected from the group consisting of cadmium (Cd), mercury (Hg), gallium (Ga), indium (In), germanium (Ge), tin (Sn), lead (Pb), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S), selenium (Se), tellurium (Te), and polonium (Po).

[0037] The one or more additional elements or compounds adapted to adjust the surface tension of the molten weld metal can adjust, e.g., reduce, the surface tension of the molten weld metal droplet so that the molten droplet detaches from the electrode at a faster rate than a metal droplet formed from a reference electrode that does not include the one or more additional elements or compounds adapted to adjust the surface tension of the molten weld metal. The droplet size can be related to the equilibrium contact angle of the droplet formed on the solidified weld metal or workpiece, as defined by a relationship known as the Young-Dupre equation. The solid-gas interfacial energy between the molten weld metal and the workpiece can be expressed as γ SG and the solid-liquid interfacial energy is expressed as γ SL and the liquid-gas interfacial energy (i.e., surface tension) is expressed as γ LG When expressed as, the equilibrium contact angle θ C is determined from these quantities by the Young-Dupre equation: gamma SG -γ SL -γ LG ×cosθ C =0

[0038] That is, the contact angle is established by a balance of adhesive forces (the liquid trying to maintain contact with the solid) and cohesive forces within the liquid (both internal cohesive forces and surface tension). Increasing adhesive forces between the liquid and the solid or decreasing cohesive forces (surface tension) within the liquid results in increased wettability and a smaller contact angle. At higher travel speeds, lower surface tension can be advantageous due to reduced droplet size and improved wetting of the workpiece or solidified weld metal by the molten weld metal. For example, the average droplet size formed from electrodes according to embodiments may be reduced by 30%, 40%, 50%, 60%, or a value within a range defined by any of these values ​​with the addition of these elements. The surface tension of molten droplets formed from a welding electrode may be reduced by 10%, 20%, 30%, 40%, 50%, or more compared to reference molten droplets formed under the same welding conditions from a reference welding electrode that is identical to the welding electrode except for the presence of the surface tension-modifying element. The average droplet size and surface tension can be reduced such that the travel speed for forming the weld metal using a welding electrode according to an embodiment can be 30%, 40%, 50%, 60%, or more higher than the travel speed for forming the weld metal without a welding electrode that does not include one or more additional elements or compounds adapted to adjust the surface tension of the molten weld.

[0039] The inventors have discovered that one or more additional elements or compounds adapted to adjust the surface tension of the molten weld metal can synergistically and simultaneously reduce the amount of slag or residual oxide or silicate islands that form on the weld metal. Oxide islands can be difficult to remove and can degrade the visual appearance of the weld metal. The relative ease of removal of oxide or silicate islands can be related to the equilibrium contact angle of the oxide or silicate islands that form on the weld metal, as defined by a relationship known as the Young-Dupre equation. The solid-gas interfacial energy can be expressed as γ SG and the solid-liquid interfacial energy is expressed as γ SL and the liquid-gas interfacial energy (i.e., surface tension) is expressed as γ LG When expressed as, the equilibrium contact angle θ Cis determined from these quantities by the Young-Dupre equation, also defined above, i.e., the same equation may be applicable, but the relevant interface is the interface between the silicate islands and the underlying weld metal.

[0040] According to embodiments, the one or more additional elements or compounds adapted to adjust the surface tension of the molten weld metal are present in an amount and form such that the volume of silica islands formed on the weld metal formed from the welding wire is at least 30%, 40%, 50%, 60%, or more lower than the volume of silica islands formed on the weld metal formed from a core wire that does not include the one or more additional elements or compounds adapted to adjust the surface tension of the molten weld.

[0041] According to various embodiments, each of the one or more conductive elements or compounds and the additional element or compound is present in an amount greater than 0.0005 wt.%, 0.0010 wt.%, 0.0020 wt.%, 0.0050 wt.%, 0.010 wt.%, 0.020 wt.%, 0.050 wt.%, 0.10 wt.%, 0.20 wt.%, 0.5 wt.%, 1.0 wt.%, 2.0 wt.%, 5.0 wt.% of the weight of the welding wire, or a value within a range defined by any of these values.

[0042] Thus, the welding wire includes a core wire having an Fe-based or steel composition, e.g., a mild steel composition, that includes Fe, one or more of C, Mn, Si, Ni, Mo, Cr, and V, one or more conductive elements or compounds, and additional elements or compounds at concentrations above impurity levels. Core wire, as used herein, refers to a solid wire having a substantially homogeneous composition.

[0043] 4B, in some embodiments, two of the first coating 308A, the second coating 308B, and the third coating 308C are configured as conductive coatings. For example, the first coating 308A and the third coating 308C may be the same or different conductive coatings and may be interleaved with the second coating 308B disposed as an additional functional coating.

[0044] 4B, in some other embodiments, two of the first coating 308A, the second coating 308B, and the third coating 308C are configured as additional functional coatings. For example, the first coating 308A and the third coating 308C may be the same or different additional functional coatings and may be interleaved by the second coating 308B, which is disposed as a conductive coating.

[0045] 3 and 4A-4B, according to various embodiments, core wire 304 may have a diameter of 1 / 16 inch (1.6 mm), 3 / 32 inch (2.5 mm), 1 / 8 inch (3.2 mm), 5 / 32 inch (4.0 mm), 3 / 16 inch (5.0 mm), or a diameter within a range defined by any of these values, e.g., 3.2 mm. Core wire 304 may have a length of 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, or a length within a range defined by any of these values. Coating 308 may have a thickness of 1-1.5 mm, 1.5-2.0 mm, 2.0-2.5 mm, 2.5-3.0 mm, or a thickness within a range defined by any of these values, e.g., 1.2 mm. By way of example only, an electrode having a 3.2 mm core wire diameter and a 1.2 mm coating thickness may have an overall diameter of 5.6 mm, and an electrode having a 4.0 mm core wire diameter and a 1.35 mm coating thickness may have an overall diameter of 6.7 mm. According to various embodiments, the coating 308 may have a weight percentage of 10-15%, 15-20%, 20-25%, 25-30%, 30-35%, 35-40%, or a value within a range defined by any of these values, based on the total weight of the electrode 300.

[0046] In certain embodiments, additional functional coating 308B is formed on conductive coating 308A. When additional functional coating 308B includes a molten weld metal surface tension modifier, it includes one or both of elemental antimony (Sb) and one or more Sb oxides. The one or more Sb oxides may be diantimony tetroxide (Sb2O4), antimony trioxide (Sb2O3), antimony pentoxide (Sb2O5), antimony hexoxide (Sb6O 13 ), and antimonite (Sb3O6(OH)). Substoichiometric oxides of these oxides are also possible.

[0047] The inventors have discovered that, for various reasons described herein, it can be particularly advantageous to form the additional functional coating 308B, including Sb, by electrochemical deposition techniques. The electrode structures described herein, including a solid core wire coated with two or more functional coatings, are particularly advantageous for electrodeposition because the underlying solid core wire 304 or conductive coating 308A can function as an effective electrode for the associated electrochemical reaction. This is in contrast to electrodes with discontinuous or poorly conductive cores, such as those formed from powders, e.g., metal-cored electrodes.

[0048] The inventors have further discovered that forming the Sb-containing additional functional coating 308B by electrochemical deposition can be particularly advantageous because it can provide a high degree of control over composition at both the macroscopic and microscopic levels. In particular, electrodeposition allows for the formation of elemental antimony (Sb) and / or one or more Sb oxides. In one particular example, for example, an additional functional coating containing Sb particles and one or more Sb oxides can be deposited by the galvanostatic reduction of antimony tartrate. Using such an electrodeposition technique, a composite film containing elemental antimony (Sb) and / or one or more Sb oxides can be formed. The relative amounts of Sb and / or Sb oxides can be controlled so that the overall composition of the resulting Sb / Sb oxide mixture can have an Sb:O ratio of 0.1, 0.2, 0.5, 1, 2, 5, 10, or a value within a range defined by any of these values.

[0049] In some embodiments, the resulting film may be a homogeneous mixture of elemental Sb and Sb oxide. In other embodiments, the resulting additional functional coating 308B may include islands, domains, grains, or particles that may include any one or more of elemental Sb and / or Sb oxide. As an example, the relative amounts of elemental Sb and Sb oxide, e.g., elemental Sb particles and Sb oxide particles, may be controlled by controlling the local pH at the electrode / electrolyte interface. The intermediate product of a welding electrode having a solid-core wire covered with a conductive coating, e.g., a Cu coating, can function as an electrode in these electrochemical reactions. Without being bound by any theory, Sb is thermodynamically stable at low pH, while the formation of SbO is favored at higher pH values. Therefore, by controlling the pH at the electrode / electrolyte interface, the additional functional coating may have a controlled amount of Sb particles and one or more Sb oxide particles. Furthermore, depending on the initial pH of the electrode / electrolyte interface, the additional functional coating 308B can be controlled to have an initial nucleation layer that is predominantly or predominantly comprised of one or the other of elemental Sb and Sb oxide. Using these and other techniques, the weight ratio of elemental Sb particles to Sb oxide particles can be controlled to 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or a value within a range defined by any of these values.

[0050] The inventors have further discovered that it can be particularly advantageous to form the additional functional coating 308B including Sb by electrochemical deposition, which provides control over the morphology of the additional functional coating. In particular, the inventors have discovered that it can be advantageous to form the coating using submicron particles, which can provide a high degree of control over the morphology of the resulting coating at both the macroscopic and microscopic levels. By controlling the surface condition of the underlying conductive coating, such as a Cu coating formed on a solid core wire, the nucleation density can be controlled in the electrochemical deposition of elemental Sb and Sb oxides. For example, by providing a rougher underlying surface, a higher nucleation density can be achieved, which results in a smaller average island, domain, grain, or particle size. The average island, domain, grain, or particle size can be less than 1000 nm, less than 800 nm, less than 600 nm, less than 400 nm, less than 200 nm, less than 100 nm, less than 50 nm, less than 20 nm, less than 10 nm, or a value within a range defined by any of these values.

[0051] The islands, domains, grains, or particles can have a controlled shape and average size and size distribution so that the resulting additional functional coating 308B has a controlled porosity. Controlling the porosity can be advantageous for a variety of reasons, including physical appearance, improved adhesion with overlying coatings, and controlled exposure of underlying materials, to name a few. For example, the porosity, defined as the ratio of void volume to the total volume of the coating, can be controlled to 0.1, 0.2, 0.3, 0.4, 0.5, or a value within a range defined by any of these values.

[0052] Furthermore, in some embodiments, the additional functional coating 308B may be discontinuous, sparse, or otherwise formed to partially cover the underlying solid core wire 304 or conductive coating 308A. Partial coverage may be beneficial in some circumstances, for example, to optimize the surface friction and travel speed of the welding wire. For example, if the underlying conductive coating 308A, such as a Cu coating, has substantially lower friction, it may be desirable to partially expose the conductive coating 308A. The surface coverage, defined as the ratio of the surface area of ​​the underlying material covered by the additional functional coating 308B to the total surface area of ​​the underlying material (e.g., conductive coating 308A), may be controlled to 0.1, 0.2, 0.3, 0.4, 0.5, or a value within a range defined by any of these values.

[0053] The inventors have discovered that it may be advantageous to configure a welding wire so that a controlled amount of Sb becomes part of the weld metal to enhance the surface tension-reducing effect of Sb while reducing the potential for Sb to adversely affect the mechanical properties of the resulting weld metal. According to embodiments, the amount of Sb in the welding electrode that alloys with the weld metal may be less than 60%, less than 50%, less than 40%, less than 30%, or less than 20% of the total amount of Sb present in the welding wire, e.g., 25-60% of the total amount of Sb present in the welding wire. The relatively small amount of Sb incorporated into the weld metal is due to various features of the additional functional coating 308B described above, including the presence of both elemental Sb and Sb oxides, which may be made possible by electrochemical deposition. Various amounts of Sb can be volatilized, for example, by controlling the ratio of elemental Sb to Sb oxides. Table 1 below shows the experimental atomic % of Sb in experimentally produced welding wires and the atomic % of Sb detected in the resulting weld metal. As shown, 0.009-0.024% Sb in the welding wire results in 0.004-0.010% Sb in the resulting weld metal.

[0054] [Table 1]

[0055] Method for manufacturing coated electrodes FIG. 5 illustrates a method 500 for forming two or more coatings on a core wire, according to an embodiment. The method 500 includes providing (510) a core wire 304 (FIGS. 4A and 4B) having a base metal composition and conditioning (520) the surface of the core wire in preparation for forming the two or more coatings. The method 500 includes forming (530) a first coating 308A (FIGS. 4A and 4B) including one of a conductive coating including one or more conductive elements or compounds in addition to or other than copper (Cu) and an additional functional coating. After forming (530) the first coating 308A, the method 500 proceeds to postconditioning (540) the surface of the first coating 308A. The method 500 further includes forming (550) a second coating 308B (FIGS. 4A and 4B) including the other of the conductive coating and the additional functional coating. After forming (550) the second coating 308B, the method 500 proceeds with post-conditioning (560) the surface of the second coating 308B.

[0056] In some embodiments, the method 500 optionally proceeds to forming (540) a third coating 308C (FIG. 4B). In some embodiments, the third coating 308C may be a second conductive coating that includes one or more conductive elements or compounds in addition to or other than copper (Cu). In some other embodiments, the third coating 308C may be a second, additional functional coating that is different from the first functional coating.

[0057] As noted above, either the first coating 308A or the second coating 308B of electrode 400A (FIG. 4A), or either the first coating 308A, the second coating 308B, and the third coating 308C of electrode 400B (FIG. 4B), can be disposed in any order as either a conductive coating or an additional functional coating.

[0058] The method 500 can be performed on a production line including a loading station for providing (510) a core wire, a surface conditioning station for conditioning (520) the core wire, a drawing station, a first coating station for forming (530) a first coating, a first postconditioning station for postconditioning (540) the surface of the first coating, a second coating station for forming (550) a second coating, a second postconditioning station for postconditioning (560) the surface of the second coating, a third coating station for forming (570) a third coating, and a third postconditioning station for postconditioning (580) the surface of the third coating.

[0059] Providing 510 a core wire includes providing a core wire 304 (FIGS. 3, 4A-4B) including a base metal composition as described above, e.g., a steel composition such as a mild steel composition. Conditioning 520 the surface of the core wire includes cleaning the surface at a cleaning station. In one exemplary embodiment, the cleaning station uses a cleaning agent and / or coating agent to clean the outer surface of the material.

[0060] After cleaning, the material moves to a drawing station, which includes at least one die. In one exemplary embodiment, the drawing station includes a series of dies, each with a successively smaller opening than the previous die. A lubricant (e.g., a powdered lubricant) may be added to the die to facilitate passage of the core wire through the dies and reduce die wear. As the core wire passes through the drawing station, the diameter of the material can be gradually reduced to the desired dimension by plastic deformation. In some embodiments, the drawing process uses drawing soap, which may be a stearate salt, such as calcium stearate, sodium stearate, or the like. These soaps aid in the drawing process. After the drawing step, the core wire may further pass through an acid bath to further clean the incoming core wire and prepare it for forming one or more coatings thereon. After cleaning, the desired Ca range on the wire is such that the wire can be further used for coating. The Ca content can vary from 0.0005 wt% to 1 wt% of the wire to create an optimized surface for further coatings.

[0061] After conditioning (520) the surface of the core wire, the method 500 proceeds to forming (530) a first coating 308A (FIGS. 4A, 4B) that includes a conductive coating that includes one or more conductive elements or compounds in addition to or other than copper (Cu), and an additional functional coating, such as one of the Sb-containing coatings described herein.

[0062] In various embodiments, forming the first coating (530) includes, for example, wet coating in a wire plating bath containing the desired coating recipe. The wet coating process can be performed by a chemical / electrochemical or mechanical / physical process. Chemical processes can be displacement reactions, sol-gel thin film processes, electroplating, or electroless plating, to name a few. In mechanical / physical processes, the coating is adhered to the wire surface using a binder.

[0063] After forming (530) the first coating 308A, the method 500 proceeds to postconditioning (540) the surface of the first coating 308A. In some examples, postconditioning 540 includes curing using, for example, in-line heating. In-line heating can be achieved by conduction, convection, radiation, or Joule heating, etc. Heating can also be electrical / resistance heating, induction heating, heating by flame or hot air, laser heating, plasma heating, etc.

[0064] The method 500 further includes forming 550 a second coating 308B (FIGS. 4A, 4B) including the other of the conductive coating and the additional functional coating. In various embodiments, forming 550 the second coating includes wet coating, for example, in a wire plating bath including the desired coating recipe. The wet coating process can be performed by a chemical / electrochemical or mechanical / physical process. The chemical process can be a displacement reaction, a sol-gel thin film process, electroplating, or electroless plating, to name a few. In a mechanical / physical process, the coating is adhered to the wire surface using a binder.

[0065] If present, method 500 includes forming one or more additional coatings 308C (FIG. 4B), which may be similar to forming first coating 308A (530) and / or forming second coating 308B (550).

[0066] It will be appreciated that in some embodiments, one or both of the conductive coating and the additional functional coating comprise a plurality of pores, the pores being at least partially filled with a material different from the porous conductive coating and the additional functional coating. If present, having a porous structure can be advantageous for improving adhesion between the different layers.

[0067] After forming (550) the second coating 308B, the method 500 proceeds to postconditioning (560) the surface of the second coating 308B. In some embodiments, postconditioning 560 includes passing through a finishing / polishing die. If the final coating includes a metallic coating, such as a Cu coating, the polishing die smooths the wire surface, removes excess copper, and makes the wire appear uniform and shiny, among other effects. The die may be a polycrystalline diamond die or a tungsten carbide die.

[0068] FIG. 6A shows a weld metal formed using a conventional consumable electrode. FIG. 6B shows a weld metal formed using a consumable electrode having a functional coating according to an embodiment. The two consumable electrodes used to form the weld metals of FIGS. 6A and 6B have the same composition except for the functional coating. In particular, the weld metal shown in FIG. 6B was formed using an electrode having a conductive coating including one or more conductive elements including copper (Cu) and an additional functional coating formed on the conductive coating and including elemental antimony (Sb) and one or more Sb oxides. As described above with respect to FIG. 4A, the weld metal formed using a consumable electrode according to an embodiment has a dramatically reduced amount of silicate islands due to an increased contact angle between the silicate islands and the weld metal.

[0069] Further Example Embodiments 1. A core wire having a base metal composition; two or more coatings covering at least a portion of the core wire, the two or more coatings comprising: a conductive coating comprising one or more conductive elements or compounds in addition to or other than copper (Cu); an additional functional coating comprising one or more additional elements or compounds adapted to reduce friction of the welding electrode, stabilize the arc formed from the welding electrode, adjust the microstructure of the weld metal formed from the welding electrode, and / or adjust the surface tension of the molten droplets formed from the welding electrode; and two or more coatings, , a welding electrode. 2. The welding electrode of embodiment 1, wherein the one or more conductive elements or compounds are selected from the group consisting of magnesium (Mg), aluminum (Al), zinc (Zn), tin (Sn), chromium (Cr), platinum (Pt), silver (Ag), graphite, graphene, graphene oxide, and titanium (Ti). 3. The welding electrode of embodiment 1 or 2, wherein the one or more conductive elements or compounds are present without Cu. 4. The welding electrode of embodiment 1 or 2, wherein the one or more conductive elements or compounds, in addition to Cu, are present in an amount greater than 90 atomic % of the sum of the one or more conductive elements or compounds and Cu. 5. The welding electrode of any one of embodiments 1-4, wherein the one or more conductive elements or compounds are present in an amount and form such that the welding electrode has a lower electrical resistance compared to a core wire that does not contain the conductive elements or compounds. 6. The welding electrode of any one of embodiments 1-5, wherein the additional functional coating comprises one or more additional elements or compounds adapted to reduce friction of the welding electrode selected from the group consisting of graphite, metal sulfides, polytetrafluoroethylene, graphene, and graphene oxide. 7. The welding electrode of embodiment 6, wherein the metal sulfide is molybdenum disulfide (MoS2) or tungsten disulfide (WS2). 8. A welding electrode according to any one of embodiments 1 to 7, wherein the one or more additional elements or compounds adapted to reduce friction are present in an amount and form such that a wire feeding force for feeding the welding wire through the wire liner is at least 50% lower than a wire feeding force for feeding a core wire that does not include the one or more additional elements or compounds adapted to reduce friction. 9. The welding electrode of any one of embodiments 1-8, wherein the additional functional coating comprises one or more additional elements or compounds adapted to stabilize an arc formed from the welding electrode selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), cerium (Ce), barium (Ba), and radium (Ra). 10. The welding electrode of any one of embodiments 1-9, wherein the one or more additional elements or compounds adapted to stabilize the arc are present in an amount and form such that one or both of an oxygen content and a nitrogen content of a weld metal formed from the welding wire is at least 50% lower than a weld metal formed from a core wire that does not include the one or more additional elements or compounds adapted to stabilize the arc. 11. The welding electrode of any one of embodiments 1-10, wherein the additional functional coating comprises one or more additional elements or compounds adapted to adjust the microstructure of the weld metal formed from the welding electrode, selected from the group consisting of titanium (Ti), zirconium (Zr), nickel (Ni), boron (B), molybdenum (Mo), and niobium (Nb). 12. The welding electrode of any one of embodiments 1-11, wherein the one or more additional elements or compounds adapted to modify the microstructure are present in an amount and form such that the impact toughness of a weld metal formed from the welding wire is at least 50% greater than a weld metal formed from a core wire that does not include the one or more additional elements or compounds adapted to modify the microstructure. 13. The welding electrode of any one of embodiments 1-12, wherein the one or more additional elements or compounds adapted to modify the microstructure are present in an amount and form such that the ductile-to-brittle transition temperature of a weld metal formed from the welding wire is at least 50°C lower than a weld metal formed from a core wire that does not include the one or more additional elements or compounds adapted to modify the microstructure. 14. The welding electrode of any one of embodiments 1-13, wherein the additional functional coating comprises one or more elements or compounds adapted to adjust the surface tension of the molten droplets selected from the group consisting of cadmium (Cd), mercury (Hg), gallium (Ga), indium (In), germanium (Ge), tin (Sn), lead (Pb), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), sulfur (S), selenium (Se), tellurium (Te), and polonium (Po). 15. The welding electrode of any one of embodiments 1-14, wherein the one or more additional elements or compounds adapted to adjust the surface tension of the molten weld are present in an amount and form such that the welding electrode is configured to form a weld metal at a travel speed that is at least 30% higher than a travel speed for forming a weld metal that does not include the one or more additional elements or compounds adapted to adjust the surface tension of the molten weld. 16. A welding electrode according to any one of embodiments 1 to 15, wherein the one or more additional elements or compounds adapted to adjust the surface tension of the molten weld are present in an amount and form such that the volume of silica islands formed on the weld metal formed from the welding wire is at least 50% lower than the volume of silica islands formed on the weld metal formed from a core wire that does not include the one or more additional elements or compounds adapted to adjust the surface tension of the molten weld. 17. A welding electrode according to any one of embodiments 1 to 16, wherein one or both of the conductive coating and the additional functional coating include a plurality of pores, and the pores are at least partially filled with a material different from the conductive coating and the additional functional coating having the pores. 18. A welding electrode according to any one of embodiments 1 to 17, wherein one or both of the conductive coating and the additional functional coating are porous or intermixed such that the conductive elements and the additional functional material at least partially interpenetrate each other in at least a direction perpendicular to the surface of the core wire. 19. A welding electrode according to any one of embodiments 1 to 18, wherein the conductive coating and the additional functional coating are continuous layers having a clearly detectable boundary formed therebetween. 20. The welding electrode of any one of embodiments 1-19, wherein at least some of the different additional elements or compounds of the one or more additional elements or compounds adapted to reduce friction of the welding electrode, stabilize an arc formed from the welding electrode, adjust the microstructure of a weld metal formed from the welding electrode, and adjust the surface tension of molten droplets formed from the welding electrode are disposed in different coatings of the two or more coatings. 21. The welding electrode of any one of embodiments 1 to 20, wherein each of the one or more conductive elements or compounds and the additional element or compound is present in an amount of 0.0005 to 5 wt.% of the weight of the welding wire. 22. The welding electrode of any one of embodiments 1-21, further comprising calcium (Ca) in an interface region between the core wire and the two or more coating layers. 23. The welding electrode of any one of embodiments 1-22, further comprising calcium (Ca) in an interface region between the core wire and the two or more coating layers in an amount of 0.0005-1 wt.% of the weight of the welding wire. 24. The welding electrode of any one of embodiments 1-23, wherein the two or more coatings further include a second conductive coating that includes one or more conductive elements or compounds in addition to or other than copper (Cu). 25. The welding electrode of embodiment 24, wherein an additional functional coating is interposed between the conductive coating and the second conductive coating. 26. The welding electrode of any one of embodiments 1-24, wherein the two or more coatings further include a second additional functional coating including one or more additional elements or compounds adapted to reduce friction of the welding electrode, stabilize an arc formed from the welding electrode, adjust the microstructure of the weld metal formed from the welding electrode, and / or adjust the surface tension of molten droplets formed from the welding electrode. 27. The welding electrode of embodiment 26, wherein the conductive coating is interposed between the additional functional coating and the second additional functional coating. 28. A method for manufacturing a welding electrode according to any one of embodiments 1 to 23, comprising: providing a core wire having a base metal composition; forming two or more coatings, including forming a conductive coating and forming an additional functional coating; A method comprising: 29. The method of embodiment 28, wherein one or both of forming the conductive coating and forming the additional functional coating is performed by a chemical reaction or an electrochemical reaction. 30. The method of embodiment 28 or 29, wherein one or both of forming the conductive coating and forming the additional functional coating is performed using a dip coating process. 31. The method of any one of embodiments 28 to 30, wherein one or both of forming the conductive coating and forming the additional functional coating are performed using one or more of a displacement reaction, a sol-gel thin film process, electroplating, and electroless plating. 32. The method of embodiment 28, wherein one or both of forming the conductive coating and forming the additional functional coating is performed using a physical or mechanical deposition process. 33. The method of any one of embodiments 28-32, wherein one or both of forming the conductive coating and forming the additional functional coating are performed sequentially in different process stations. 34. The method of any one of embodiments 28-23, wherein one or both of forming the conductive coating and forming the additional functional coating are performed simultaneously in the same process station. 35. The method of any one of embodiments 28-34, further comprising conditioning the outer surface of the core wire with a compound containing calcium (Ca) before forming the two or more coating layers.

[0070] Unless the context clearly requires otherwise, throughout this specification and claims, words such as "comprise," "comprising," "include," "including," and the like are intended to be interpreted in an inclusive sense, i.e., "including, but not limited to," as opposed to an exclusive or exhaustive sense. The term "coupled," as generally used herein, refers to two or more elements that may be directly connected or that may be connected through one or more intermediate elements. Similarly, the term "connected," as generally used herein, refers to two or more elements that may be directly connected or that may be connected through one or more intermediate elements. Furthermore, the words "herein," "above," "below," and words of similar import, when used in this application, refer to this application as a whole and not to any particular portions of this application. Where the context allows, words in the above Detailed Description using the singular or plural number may also include the plural or singular number, respectively. The word "or" in reference to a list of two or more items covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list.

[0071] Additionally, conditional language used herein, such as "can," "could," "might," "e.g.," "for example," and "such as," among others, is generally intended to convey that certain embodiments include particular features, elements, and / or conditions, and that other embodiments do not include those particular features, elements, and / or conditions, unless specifically stated otherwise or understood otherwise within the context in which it is used. Thus, such conditional language is generally not intended to imply that features, elements, and / or conditions are in any way required for one or more embodiments, or that those features, elements, and / or conditions may or may not be included in or practiced in a particular embodiment.

[0072] While specific embodiments have been described, these embodiments are presented by way of example only and are not intended to limit the scope of the present disclosure. Indeed, the novel apparatus, methods, and systems described herein may be embodied in a variety of other forms, and various omissions, substitutions, and changes in the form of the methods and systems described herein may be made without departing from the spirit of the present disclosure. For example, while blocks are presented in a given arrangement, alternative embodiments may perform similar functions using different components and / or circuit topologies, and some blocks may be deleted, moved, added, subdivided, combined, and / or modified. Each of these blocks may be implemented in a variety of different ways. Any appropriate combination of elements and acts of the various embodiments described above may be combined to provide further embodiments. The various features and processes described above may be implemented independently of each other or combined in various ways. All possible combinations and subcombinations of features of the present disclosure are intended to fall within the scope of the present disclosure.

Claims

1. a solid core wire having an iron (Fe) based base metal composition; a conductive coating formed on the solid core wire and including one or more conductive elements or compounds in addition to or other than copper (Cu); an additional functional coating formed on the conductive coating, the additional functional coating comprising one or more additional elements or compounds selected from the group consisting of graphite, metal sulfide, polytetrafluoroethylene, graphene, and graphene oxide; and A welding electrode comprising:

2. The welding electrode of claim 1 , wherein the one or more additional elements or compounds include a metal sulfide.

3. The metal sulfide is molybdenum disulfide (MoS ２ ) or tungsten disulfide (WS ２ 3. The welding electrode of claim 2, comprising:

4. The welding electrode of claim 2 , wherein the metal sulfide has a layered structure.

5. The welding electrode of claim 1 , wherein the one or more additional elements or compounds are adapted to reduce friction between the welding electrode and a wire liner.

6. 5. The welding electrode of claim 4, wherein the one or more additional elements or compounds are compounds adapted to reduce friction and are present in an amount and form such that a wire feed force for feeding the welding electrode through a wire liner is at least 50% lower than a wire feed force for feeding a reference welding electrode that is identical to the welding electrode except for the presence of the additional functional coating.

7. 10. The welding electrode of claim 1, wherein the one or more conductive elements or compounds are selected from the group consisting of magnesium (Mg), aluminum (Al), zinc (Zn), tin (Sn), chromium (Cr), platinum (Pt), silver (Ag), graphite, graphene, graphene oxide, and titanium (Ti).

8. The welding electrode of claim 7 , wherein the one or more conductive elements or compounds are present in the conductive coating without including Cu.

9. 8. The welding electrode of claim 7, wherein the one or more conductive elements or compounds are present in an amount in addition to Cu that is greater than 90 atomic % of the sum of the one or more conductive elements or compounds and Cu.

10. The welding electrode of claim 1 , wherein the Fe-based base metal composition comprises a stainless steel composition.

11. a solid core wire having an iron (Fe) based base metal composition; two or more coatings covering at least a portion of the solid core wire, the two or more coatings comprising: a conductive coating formed on the solid core wire, the conductive coating including one or more conductive elements or compounds in addition to or other than copper (Cu); an additional functional coating comprising one or more additional elements or compounds selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), cerium (Ce), barium (Ba), and radium (Ra); two or more coatings, A welding electrode comprising:

12. The welding electrode of claim 11 , wherein the one or more additional elements or compounds are adapted to stabilize an arc formed from the welding electrode.

13. 13. The welding electrode of claim 12, wherein the one or more additional elements or compounds are present in a quantity such that one or both of an oxygen content and a nitrogen content of a weld metal formed from the welding electrode is at least 50% lower than one or both of an oxygen content and a nitrogen content of a reference weld metal formed from a reference welding electrode that is identical to the welding electrode except for the presence of the additional functional coating.

14. The welding electrode of claim 11 , wherein the Fe-based base metal composition comprises a stainless steel composition.

15. 12. The welding electrode of claim 11, wherein the one or more conductive elements or compounds are selected from the group consisting of magnesium (Mg), aluminum (Al), zinc (Zn), tin (Sn), chromium (Cr), platinum (Pt), silver (Ag), graphite, graphene, graphene oxide, and titanium (Ti).

16. a solid core wire having an iron (Fe)-based base metal composition; a conductive coating formed on the solid core wire and including one or more conductive elements or compounds in addition to or other than copper (Cu); an additional functional coating formed on the conductive coating, the additional functional coating comprising one or more additional elements or compounds selected from the group consisting of titanium (Ti), zirconium (Zr), nickel (Ni), boron (B), molybdenum (Mo), and niobium (Nb); and A welding electrode comprising:

17. The welding electrode of claim 16 , wherein the one or more additional elements or compounds include Mo.

18. 17. The welding electrode of claim 16, wherein the one or more additional elements or compounds are adapted to adjust the microstructure of a weld metal formed from the welding electrode such that the impact toughness of the weld metal is greater than the impact toughness of a weld metal formed from a reference welding electrode that is the same as the welding electrode except for the presence of the additional functional coating.

19. 20. The welding electrode of claim 18, wherein the one or more additional elements or compounds are present in an amount and form such that the impact toughness of the weld metal is increased by 50% or more compared to the weld metal formed from the reference welding electrode.

20. 17. The welding electrode of claim 16, wherein the one or more additional elements or compounds are adapted to adjust the microstructure of the weld metal such that the ductile-to-brittle transition temperature of the weld metal is lower than the ductile-to-brittle transition temperature of a weld metal formed from a reference welding electrode that is identical to the welding electrode except for the presence of the additional functional coating.

21. 21. The welding electrode of claim 20, wherein the one or more additional elements or compounds are present in an amount and form such that the ductile-to-brittle transition temperature of the weld metal is at least 50°C lower than the weld metal formed from the reference welding electrode.

22. 17. The welding electrode of claim 16, wherein the one or more conductive elements or compounds are selected from the group consisting of magnesium (Mg), aluminum (Al), zinc (Zn), tin (Sn), chromium (Cr), platinum (Pt), silver (Ag), graphite, graphene, graphene oxide, and titanium (Ti).

23. The welding electrode of claim 16, wherein the Fe-based base metal composition comprises a stainless steel composition.

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